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https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
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![Pavel Begunkov](/assets/img/avatar_default.png)
ctx is always locked for task_work now, so get rid of struct io_tw_state::locked. Note I'm stopping one step before removing io_tw_state altogether, which is not empty, because it still serves the purpose of indicating which function is a tw callback and forcing users not to invoke them carelessly out of a wrong context. The removal can always be done later. Signed-off-by: Pavel Begunkov <asml.silence@gmail.com> Tested-by: Ming Lei <ming.lei@redhat.com> Link: https://lore.kernel.org/r/e95e1ea116d0bfa54b656076e6a977bc221392a4.1710799188.git.asml.silence@gmail.com Signed-off-by: Jens Axboe <axboe@kernel.dk>
367 lines
9.1 KiB
C
367 lines
9.1 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* Support for async notification of waitid
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*/
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#include <linux/kernel.h>
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#include <linux/errno.h>
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#include <linux/fs.h>
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#include <linux/file.h>
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#include <linux/compat.h>
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#include <linux/io_uring.h>
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#include <uapi/linux/io_uring.h>
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#include "io_uring.h"
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#include "cancel.h"
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#include "waitid.h"
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#include "../kernel/exit.h"
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static void io_waitid_cb(struct io_kiocb *req, struct io_tw_state *ts);
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#define IO_WAITID_CANCEL_FLAG BIT(31)
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#define IO_WAITID_REF_MASK GENMASK(30, 0)
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struct io_waitid {
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struct file *file;
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int which;
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pid_t upid;
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int options;
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atomic_t refs;
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struct wait_queue_head *head;
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struct siginfo __user *infop;
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struct waitid_info info;
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};
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static void io_waitid_free(struct io_kiocb *req)
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{
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struct io_waitid_async *iwa = req->async_data;
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put_pid(iwa->wo.wo_pid);
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kfree(req->async_data);
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req->async_data = NULL;
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req->flags &= ~REQ_F_ASYNC_DATA;
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}
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#ifdef CONFIG_COMPAT
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static bool io_waitid_compat_copy_si(struct io_waitid *iw, int signo)
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{
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struct compat_siginfo __user *infop;
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bool ret;
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infop = (struct compat_siginfo __user *) iw->infop;
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if (!user_write_access_begin(infop, sizeof(*infop)))
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return false;
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unsafe_put_user(signo, &infop->si_signo, Efault);
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unsafe_put_user(0, &infop->si_errno, Efault);
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unsafe_put_user(iw->info.cause, &infop->si_code, Efault);
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unsafe_put_user(iw->info.pid, &infop->si_pid, Efault);
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unsafe_put_user(iw->info.uid, &infop->si_uid, Efault);
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unsafe_put_user(iw->info.status, &infop->si_status, Efault);
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ret = true;
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done:
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user_write_access_end();
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return ret;
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Efault:
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ret = false;
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goto done;
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}
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#endif
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static bool io_waitid_copy_si(struct io_kiocb *req, int signo)
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{
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struct io_waitid *iw = io_kiocb_to_cmd(req, struct io_waitid);
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bool ret;
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if (!iw->infop)
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return true;
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#ifdef CONFIG_COMPAT
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if (req->ctx->compat)
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return io_waitid_compat_copy_si(iw, signo);
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#endif
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if (!user_write_access_begin(iw->infop, sizeof(*iw->infop)))
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return false;
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unsafe_put_user(signo, &iw->infop->si_signo, Efault);
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unsafe_put_user(0, &iw->infop->si_errno, Efault);
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unsafe_put_user(iw->info.cause, &iw->infop->si_code, Efault);
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unsafe_put_user(iw->info.pid, &iw->infop->si_pid, Efault);
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unsafe_put_user(iw->info.uid, &iw->infop->si_uid, Efault);
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unsafe_put_user(iw->info.status, &iw->infop->si_status, Efault);
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ret = true;
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done:
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user_write_access_end();
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return ret;
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Efault:
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ret = false;
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goto done;
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}
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static int io_waitid_finish(struct io_kiocb *req, int ret)
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{
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int signo = 0;
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if (ret > 0) {
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signo = SIGCHLD;
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ret = 0;
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}
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if (!io_waitid_copy_si(req, signo))
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ret = -EFAULT;
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io_waitid_free(req);
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return ret;
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}
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static void io_waitid_complete(struct io_kiocb *req, int ret)
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{
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struct io_waitid *iw = io_kiocb_to_cmd(req, struct io_waitid);
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struct io_tw_state ts = {};
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/* anyone completing better be holding a reference */
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WARN_ON_ONCE(!(atomic_read(&iw->refs) & IO_WAITID_REF_MASK));
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lockdep_assert_held(&req->ctx->uring_lock);
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hlist_del_init(&req->hash_node);
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ret = io_waitid_finish(req, ret);
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if (ret < 0)
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req_set_fail(req);
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io_req_set_res(req, ret, 0);
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io_req_task_complete(req, &ts);
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}
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static bool __io_waitid_cancel(struct io_ring_ctx *ctx, struct io_kiocb *req)
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{
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struct io_waitid *iw = io_kiocb_to_cmd(req, struct io_waitid);
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struct io_waitid_async *iwa = req->async_data;
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/*
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* Mark us canceled regardless of ownership. This will prevent a
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* potential retry from a spurious wakeup.
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*/
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atomic_or(IO_WAITID_CANCEL_FLAG, &iw->refs);
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/* claim ownership */
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if (atomic_fetch_inc(&iw->refs) & IO_WAITID_REF_MASK)
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return false;
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spin_lock_irq(&iw->head->lock);
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list_del_init(&iwa->wo.child_wait.entry);
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spin_unlock_irq(&iw->head->lock);
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io_waitid_complete(req, -ECANCELED);
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return true;
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}
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int io_waitid_cancel(struct io_ring_ctx *ctx, struct io_cancel_data *cd,
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unsigned int issue_flags)
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{
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struct hlist_node *tmp;
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struct io_kiocb *req;
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int nr = 0;
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if (cd->flags & (IORING_ASYNC_CANCEL_FD|IORING_ASYNC_CANCEL_FD_FIXED))
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return -ENOENT;
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io_ring_submit_lock(ctx, issue_flags);
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hlist_for_each_entry_safe(req, tmp, &ctx->waitid_list, hash_node) {
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if (req->cqe.user_data != cd->data &&
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!(cd->flags & IORING_ASYNC_CANCEL_ANY))
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continue;
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if (__io_waitid_cancel(ctx, req))
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nr++;
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if (!(cd->flags & IORING_ASYNC_CANCEL_ALL))
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break;
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}
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io_ring_submit_unlock(ctx, issue_flags);
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if (nr)
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return nr;
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return -ENOENT;
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}
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bool io_waitid_remove_all(struct io_ring_ctx *ctx, struct task_struct *task,
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bool cancel_all)
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{
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struct hlist_node *tmp;
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struct io_kiocb *req;
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bool found = false;
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lockdep_assert_held(&ctx->uring_lock);
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hlist_for_each_entry_safe(req, tmp, &ctx->waitid_list, hash_node) {
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if (!io_match_task_safe(req, task, cancel_all))
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continue;
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hlist_del_init(&req->hash_node);
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__io_waitid_cancel(ctx, req);
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found = true;
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}
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return found;
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}
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static inline bool io_waitid_drop_issue_ref(struct io_kiocb *req)
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{
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struct io_waitid *iw = io_kiocb_to_cmd(req, struct io_waitid);
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struct io_waitid_async *iwa = req->async_data;
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if (!atomic_sub_return(1, &iw->refs))
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return false;
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/*
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* Wakeup triggered, racing with us. It was prevented from
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* completing because of that, queue up the tw to do that.
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*/
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req->io_task_work.func = io_waitid_cb;
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io_req_task_work_add(req);
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remove_wait_queue(iw->head, &iwa->wo.child_wait);
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return true;
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}
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static void io_waitid_cb(struct io_kiocb *req, struct io_tw_state *ts)
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{
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struct io_waitid_async *iwa = req->async_data;
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struct io_ring_ctx *ctx = req->ctx;
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int ret;
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io_tw_lock(ctx, ts);
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ret = __do_wait(&iwa->wo);
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/*
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* If we get -ERESTARTSYS here, we need to re-arm and check again
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* to ensure we get another callback. If the retry works, then we can
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* just remove ourselves from the waitqueue again and finish the
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* request.
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*/
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if (unlikely(ret == -ERESTARTSYS)) {
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struct io_waitid *iw = io_kiocb_to_cmd(req, struct io_waitid);
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/* Don't retry if cancel found it meanwhile */
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ret = -ECANCELED;
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if (!(atomic_read(&iw->refs) & IO_WAITID_CANCEL_FLAG)) {
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iw->head = ¤t->signal->wait_chldexit;
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add_wait_queue(iw->head, &iwa->wo.child_wait);
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ret = __do_wait(&iwa->wo);
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if (ret == -ERESTARTSYS) {
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/* retry armed, drop our ref */
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io_waitid_drop_issue_ref(req);
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return;
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}
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remove_wait_queue(iw->head, &iwa->wo.child_wait);
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}
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}
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io_waitid_complete(req, ret);
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}
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static int io_waitid_wait(struct wait_queue_entry *wait, unsigned mode,
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int sync, void *key)
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{
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struct wait_opts *wo = container_of(wait, struct wait_opts, child_wait);
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struct io_waitid_async *iwa = container_of(wo, struct io_waitid_async, wo);
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struct io_kiocb *req = iwa->req;
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struct io_waitid *iw = io_kiocb_to_cmd(req, struct io_waitid);
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struct task_struct *p = key;
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if (!pid_child_should_wake(wo, p))
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return 0;
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/* cancel is in progress */
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if (atomic_fetch_inc(&iw->refs) & IO_WAITID_REF_MASK)
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return 1;
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req->io_task_work.func = io_waitid_cb;
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io_req_task_work_add(req);
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list_del_init(&wait->entry);
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return 1;
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}
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int io_waitid_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
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{
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struct io_waitid *iw = io_kiocb_to_cmd(req, struct io_waitid);
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if (sqe->addr || sqe->buf_index || sqe->addr3 || sqe->waitid_flags)
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return -EINVAL;
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iw->which = READ_ONCE(sqe->len);
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iw->upid = READ_ONCE(sqe->fd);
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iw->options = READ_ONCE(sqe->file_index);
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iw->infop = u64_to_user_ptr(READ_ONCE(sqe->addr2));
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return 0;
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}
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int io_waitid(struct io_kiocb *req, unsigned int issue_flags)
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{
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struct io_waitid *iw = io_kiocb_to_cmd(req, struct io_waitid);
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struct io_ring_ctx *ctx = req->ctx;
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struct io_waitid_async *iwa;
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int ret;
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if (io_alloc_async_data(req))
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return -ENOMEM;
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iwa = req->async_data;
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iwa->req = req;
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ret = kernel_waitid_prepare(&iwa->wo, iw->which, iw->upid, &iw->info,
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iw->options, NULL);
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if (ret)
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goto done;
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/*
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* Mark the request as busy upfront, in case we're racing with the
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* wakeup. If we are, then we'll notice when we drop this initial
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* reference again after arming.
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*/
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atomic_set(&iw->refs, 1);
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/*
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* Cancel must hold the ctx lock, so there's no risk of cancelation
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* finding us until a) we remain on the list, and b) the lock is
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* dropped. We only need to worry about racing with the wakeup
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* callback.
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*/
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io_ring_submit_lock(ctx, issue_flags);
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hlist_add_head(&req->hash_node, &ctx->waitid_list);
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init_waitqueue_func_entry(&iwa->wo.child_wait, io_waitid_wait);
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iwa->wo.child_wait.private = req->task;
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iw->head = ¤t->signal->wait_chldexit;
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add_wait_queue(iw->head, &iwa->wo.child_wait);
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ret = __do_wait(&iwa->wo);
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if (ret == -ERESTARTSYS) {
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/*
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* Nobody else grabbed a reference, it'll complete when we get
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* a waitqueue callback, or if someone cancels it.
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*/
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if (!io_waitid_drop_issue_ref(req)) {
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io_ring_submit_unlock(ctx, issue_flags);
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return IOU_ISSUE_SKIP_COMPLETE;
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}
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/*
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* Wakeup triggered, racing with us. It was prevented from
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* completing because of that, queue up the tw to do that.
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*/
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io_ring_submit_unlock(ctx, issue_flags);
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return IOU_ISSUE_SKIP_COMPLETE;
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}
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hlist_del_init(&req->hash_node);
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remove_wait_queue(iw->head, &iwa->wo.child_wait);
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ret = io_waitid_finish(req, ret);
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io_ring_submit_unlock(ctx, issue_flags);
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done:
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if (ret < 0)
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req_set_fail(req);
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io_req_set_res(req, ret, 0);
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return IOU_OK;
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}
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